I don't know what do you want to say but all my amp's where tested in ruff conditions a couple of hours..2 ohmi resistence(500w)pure sine wave etc...All I'm doing I'm testing .If I'm wrong it seems that a lot of Qsc, Av ,Quad ,Ampslab ,Pss audio,Technics,Pioneer(I'm not talking about quality of this amp's ;I'm talking about quantity of final transistors..) are wrong .
I don't know why you make somuch fuzz...If you don't agree nobody is stoping you tu put another pairs or two in the final stage ....
Your approach seems to me in laudatory terms in which only came in this forum.
Have a good day !

Originally posted by catalin I don't know what do you want to say but all my amp's where tested in ruff conditions a couple of hours..2 ohmi resistence(500w)pure sine wave etc...All I'm doing I'm testing .If I'm wrong it seems that a lot of Qsc, Av ,Quad ,Ampslab ,Pss audio,Technics,Pioneer(I'm not talking about quality of this amp's ;I'm talking about quantity of final transistors..) are wrong .
I don't know why you make somuch fuzz...If you don't agree nobody is stoping you tu put another pairs or two in the final stage ....
Your approach seems to me in laudatory terms in which only came in this forum.
Have a good day !

there is no reason to be upset ...here in the forum you will listen to way too many opinions ....it is obvious that some will "judge" this or any other amp versus quality or versus power or versus stability or versus theory .or or or or or .....this is endless

if your amp could fullfill all of these critiria we are talking about some miracle !!!!!!

what i personally care about is the truth ......

for example you cannot expect this amp to power up to 500w !!!!!
you cannot expect this amp to perform squarewave to 100khz!!!

and so on and on .....

i like simple amps and this is one of them ....i bet you that it has better sonics than many presented in this forum ....

You missunderstand.Not the output power was 500w.The load resistence has 500 w.I tested the resistence at 2ohms and 28 Vrms ...
I don't know why you make so much fuzz...If you don't agree nobody is stoping you to put another pairs or two in the final stage ....A couple of hours on 4 ohms speakers at full power didn't blow up anything.Beside that I rarely use this at full power.
.I will calculate the peak value !:
200W rms =4ohms*7Arms*7Arms
200W rms =(28Vrms*28Vrms)/4ohms
28Vrms ~ 40V at peak
Vce at 7Arms(10A at peak)=10V.
Pdiss peak=10V*10A=100W(peak power not rms,not continuous).
On the other hand totall power disipated by the final stage is 125Wrms at full output power(200Wrms).In that case one bipolar will disipate ~32-40 Wrms (heat).
The soa of the transistor is below .
Don't forget that the prefinall stage make an negative reaction by comparing the output voltage of the output transistor .
please correct me if I'm wrong javascript:smilie('')
Why the comercial amp's have at that Vcc 2 pairs of bipolars at 200W/4ohms.They are wrong
Have a good day !

Originally posted by catalin tested in ruff conditions a couple of hours..2 ohmi resistence(500w)pure sine wave etc...All I'm doing I'm testing .If I'm wrong it seems that a lot of Qsc, Av ,Quad ,Ampslab ,Pss audio,Technics,Pioneer(I'm not talking about quality of this amp's ;I'm talking about quantity of final transistors..) are wrong .

Sorry again if i look confused, but on the front of hundreds of audience in the open area. There's a real need of big and bigger power.

Maybe it's a right time to go away from Class A/B to another solution, in the pro Audio Application .

But Class A/B offers familiarity , simple and popular solution, rather than other class as DIY Kit or schematic available at the market.

So, If I look deeply disappointed then wildly multiply BJT, it because i have no other easy way yet.

Hi Cat,
I can model your output of 200W into 4r0 when driven from +-56Vdc, but only by reducing the smoothing capacitance to +-15mF and increasing the transformer regulation to 13.5%.

Yes, the model predicts that 2r0 can be driven to 302W and with this resistive load is just on the Tc=38degC soar. It easily drives 2r0 if you can keep the case temp below 38degC.

BUT, you have completely omitted to look at reactive loading.
The two pair 1943/5200 can produce 200W into 4ohm reactive 60degree phase angle and the peak dissipation is predicted at over 400W, 6.8Apk @ 60Vce. This is way outside the 10mS 38degC soar.
Into an 8ohm 60degree reactive load the model predicts 116W into 8r0 and the reactive maximum dissipation will be just over 200W, 3Apk @ 68Vce. This is just on the 100mS Tc=54degC soar.
This indicates to me that this 2pair output stage makes an excellent 8ohm capable amplifier.

I have another test for amp output.
The amp should deliver >=3 times the power into a load of half the spec resistance cf double the spec resistance. 117int 8r0 and 302W into 2r0 fails this test. indicating that current delivery into a reactive 4ohm load is inadequate.
But, 64W into 16r0 and 200W into 4r0 passes the >3times test, again confirming the 8ohm reactive load current driving ability.

Finally, having to change the smoothing capacitance and regulation to the values to match your measurements crippled the performance of this amplifier. It is crying out for a proper PSU. Fitting a 33Vac 400VA 4%regulation transformer with +-45mF on each channel turns your crippled output stage into a real 4ohm capable amplifier for domestic duty (the heatsink must remain cold).
My model still predicts 200W into 4r0 and on the 100mS 25degC soar when 55degree phase angle.

__________________
regards Andrew T.
Sent from my desktop computer using a keyboard

Ok ! Thank's for your feedback ! .
The others comercial amp's (up) was designed a little underrated ,no ?The engineers who design those make them underrated ?
If someone wants to listen this amp with no worries than it must 3 pairs of output devices . I must accept that the documentation about reactive load and the designing an final stage with reactive load (design about SOA vs power ) i haved miss a little.Please if you have some, maybe you can indicate to me.
I want to study all that problem in designing an proper final stage for various impedance..If you can ,give me some documentation .
Thank you again for your feedback !
A good day !

I have a little query...
When semiconductor constructors examine the SOA of a device, in which leg they place the positive voltage and in which the negative? Or in which orientation they place the DUT? In the high rail the collector and in the low the emitter, or the inverse?
I have the sense that the current during the test flows from collector to emitter because constructors reffer the measured current as Ice... is this an indication of the I course?

Originally posted by AndrewT An Nchannel FET and an NPN BJT always have the drain/collector more positive than the source/emitter.

A Pchannel FET and a PNP BJT always have the drain/collector more negative than the source/emitter.

Thanks Andrew for the reply. I had in my mind only a NPN BJT transistor when i wrote my post. Actually, you gave a confirmation that my hypothesis was right... i talk about the current course in a NPN DUT... from collector to emitter.
I will continue in a couple of hours my further thought.